I don't know if it was asked or requested before, but here i go: is there any mod to allow players to play any mission after finishing it at any time? or can such thing be done? this is a must!!!

another thing is: how can someone create in san andreas mission builder an checkpoint race, timed or not timed? i want to do three checkpoint races with the bmx, one across los santos, another one acros san fierro and los santos and the third all over the entyre san andreas. but i can't understand how to register the begining of a mission, the markers, the end and so on...